Can you please let us know the version of ADE installed in your machine?
Version 4.0.2 — I reinstalled it yesterday trying to see if that would help, but it didn't.
I'm on a Mac Air, btw.
I have the same problem too.
I used ADE 188.8.131.52411 to load 2 books from my public library onto my Kobo Touch.
Both my iMac and my Kobo are authorized with the same Adobe ID.
However, when I try to open either book I get the following message :-
Oops! This document couldn't be opened. This document is protected by Adobe Digital Rights Management (DRM) and is not currently authorized for use with your Adobe ID. Please sign in with the authorized Adobe ID and try again.
I tried deauthorizing my Kobo and tried again. But I got the same message again.
After upgrading the ADE to 4.0.2, can you please reauthorizing KOBO and try opening the book?
I did. I still have the same problem.
I have the same issue exactly. Sometimes the epub books from Toronto Public Library open on my Kobo Glo, and sometime (like now) I get the same "not authorized" message as you. I contacted Kobo support. They suggested installing an earlier version of ADE (2.0) which I did, but the error was the same. I removed and reinstalled ADE 4.02 and the problem remains.
Kobo said that it was most likely an ADE problem, but sometimes it's an issue with the library.
I have a MacBook Air running system 10.9.5
HELP!! I only have 17 days left to read my most recent library download.
I read my book on my computer in the ADE screen. It was painful, awful, and depressing.
I have the exact same problem. I have tried all the suggestions mentioned in this tread and nothing has fixed the issue. I'm getting really fed up.
I sought help from mobileread.com and their solution worked for me.
I downloaded ADE 1.7.2 and authorized it with my Adobe ID before downloading the acsm file.
Then I uploaded it onto my Kobo. I can open the book on it now.